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Патент USA US3033904

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United. States Patent 0 M
1
3,033,894
Patented May 8, 1962
2
ative thereof, or naphthalene and cyanogen are reacted in '
3,033,894
.
the presence of a catalyst consisting essentially of an an
hydrous mixture of an aluminum halide and a hydrogen
halide to produce an aryl nitrile as a principal reaction
.
PREPARATION OF BENZIL BY CATALYZED RE
ACTION OF BENZENE AND CYANOGEN
William L. Fierce, Crystal Lake, and Walter J. Sandner,
Carpentersville, IiL, assignors to The Pure Oil Com
product in high yield.
Other objects and features of this invention will become
apparent ‘from time to time throughout the speci?cation
pany, Chicago, 111., a corporation of Ohio
N0 Drawing. Filed Dec. 23, 1957, Ser. No. 704,294
10 Claims. (Cl. 260-465)
and claims as hereinafter related.
This invention is based upon our discovery that aro
This invention relates to new and useful improvements
matic hydrocarbons, such as benzene, toluene, xylene,
in processes for the preparation of aromatic 1,2-dike
tones and aryl nitriles. In particular, this invention is
based upon the discovery that benzil and benzonitrile
may be prepared in good yield by reaction of benzene
and naphthalene will react with cyanogen, in a mol ratio
greater than 2:1, in the presence of a catalyst consisting
of an anhydrous mixture of an aluminum halide and a
hydrogen halide, to produce both an aryl nitrile and an
with cyanogen in a mol ratio greater than 2:1 in the 15 intermediate compound in which the aromatic hydro
presence of a molar excess of a catalyst consisting essen—
carbon has added to both ends of the cyanogen molecule.
tially of a mixture of an aluminum halide and a hydrogen
The intermediate compound, upon hydrolysis, yields an
halide. The reaction with other aromatic hydrocarbons,
aromatic 1,2-diketone, such as benzil, tolil, naphthil or
the like. Derivatives of aromatic hydrocarbons which
such as toluene, xylene and naphthalene produces ana
logous diketones and nitriles.
20 contain functional groups which are inert toward cy
Benzil and analogous aromatic 1,2-diketones are useful
anogen and the catalyst used react in the same way as the
as chemical intermediates in the preparation of a variety
aromatic hydrocarbon and are considered to be the
equivalent thereof. In carrying out this reaction the
the oxidation of benzoin, which is in turn prepared by con
cyanogen is added in a mol ratio less than 1:2 relative
densation of two molecules of benzaldehyde in the pres 25 to the aromatic hydrocarbon, and a mol ratio less than
ence of an aqueous alkali cyanide solution. Aryl nitriles,
1:1 relative to the aluminum halide. These proportions
such as benzonitrile (C6H5CN) and to tolunitrile
of cyanogen relative to the aromatic hydrocarbon and
(CH3C6H4CN), are also useful as chemical intermediates
relative to the catalyst represent critical limits for the
in the preparation of various organic compounds. Ben
process. If the reaction is carried out using proportions
zonitrile and tolunitrile are usually prepared by reaction of 30 beyond the indicated limits an entirely different product
of organic compounds. Benzil is normally prepared by
is obtained. The following speci?c examples illustrate
the carrying out of this invention under different reac
a mono-halo toluene or benzene, such as chlorotoluene or
bromotoluene, or chlorobenzene or bromo-benzene, with
a metal cyanide such as potassium cyanide, cuprous cya-'
nide, or silver cyanide. Tolunitrile and benzonitrile may
tion conditions and using different reactants.
also be prepared by ammonolysis and dehydration of 35
toluic acid or benzoic acid.
It is one object of this invention to provide a new and
improved method for the preparation of aromatic 1,2
diketones and aryl nitriles.
Another object of this invention is to provide an im
proved method for the preparation of aromatic 1,2
Example I
A round-bottomed ?ask equipped with a stirrer and
a condenser was charged with 200 ml. of benzene and
about 56 g. of anhydrous AlCl3. The mixture was stirred
and a gaseous mixture of cyanogen (40 cc./min.) and
40 nitrogen (40 cc./min.) was bubbled in. The exit gas
was bubbled through a dilute NaOH solution to capture
any unreacted cyanogen. A total of 3.17 g. of cyanogen
diketones by reaction of cyanogen and an aromatic hydro
carbon.
was added in 35 minutes. The reaction was maintained
at ambient or room temperature. No cyanogen was
Another object of this invention is to provide an im
proved method for the preparation of aryl nitriles by reac
found in the NaOH solution, indicating complete absorp
45 tion of cyanogen by the benzene-A1013 mixture. During
tion of cyanogen and an aromatic hydrocarbon.
the addition of the cyanogen the color of the reaction
A feature of this invention is the provision of an im
mixture gradually changed from white to yellow to orange
proved process in which an aromatic hydrocarbon and
to orange-red to red-brown. Next, a gaseous mixture of
cyanogen are reacted in the presence of a catalyst con
anhydrous HCl (60 cc./min.) and nitrogen (40 ce./min.)
sisting essentially of an anhydrous mixture of an alumi
50 was bubbled into the reaction mixture. Heating was
num halide and a hydrogen halide to produce an inter
started and the mixture was re?uxed for 30 minutes while
mediate which is hydrolyzed to produce an aromatic 1,2
the nitrogen-HCI gas mixture was bubbled into it. Then
diketone.
the heating and gas flow were stopped and the reaction
Another feature of this invention is the provision of an
improved process in which benzene, or alkali derivatives 55 mixture was allowed to cool. After standing overnight,
thereof, or naphthalene is reacted with cyanogen in at
the reaction mixture was poured upon a mixture of ice
least a 2:1 mol ratio in the presence of a mixture of
and concentrated HCl. The aqueous layer from this
aluminum chloride and hydrogen chloride, at an alumi
hydrolysis step was extracted with ether, which was then
num chloride/cyanogen ratio greater than 1, to produce
combined with the benzene layer and washed with water
an intermediate product which is hydrolyzed to produce 60 until free of acid. The ether and benzene were than
evaporated, leaving 7.05 g. of crude product. The pres
an aromatic 1,2-diketone, such as benzil or an analogue
thereof.
ence of benzil in this crude material was veri?ed quali
A further feature of this invention is the provision of
tatively by recrystallizing a portion of it twice from
an improved process in which benzene, or an alkyl deriv
aqueous alcohol. Light yellow crystals were obtained
3,033,894
4
evaporated to give 100 ml. of a dark brown, liquid-solid
slurry. The product was analyzed by infrared analysis
which melted at 91 ° C. (pure benzil melts at 95 ° C.) . The
benzil was further characterized by formation of a 2,4- .
dinitrophenylhydrazone derivative which had a melting
and contained p-tolunitrile in an amount equal to a yield
point corresponding to the known benzil-2,4-dinitro~
phenylhydrazone derivative. The yield of the derivative,
of about 65%. The remainder of the product is prin
cipally p,p-dimethyl benzil, also known as tolil.
8.55 g., indicated that the yield of puri?ed product was
36.0%, and that the purity of the crude product was
65.7%.
Example VI 7
In another experiment the procedure of Example I was
followed except that an equal molar amount of xylene was
Example II
substituted for the benzene. Following this procedure a
In another experiment benzil was prepared following 10 substantial amount of liquid product was obtained which
substantially the same procedure used in Example I. ‘In
contains a substantial yield of xylil (tetramethyl benzil)
this experiment 3.34 g. of cyanogen were bubbled into
and xylonitrile (dimethyl benzonitrile).
the benzene-AlCL, mixture. The procedure in this case
di?ered in that the I-ICl was bubbled into the reaction
mixture before (instead of during) the re?uxing step.
Example VII
15
In still a further experiment cyanogen and hydrogen
The benzil yield in this case was slightly lower. There
was, obtained 4.82 g. of crude product which produced
chloride were bubbled into a suspension of aluminum
chloride in a ‘solution of naphthalene in carbon disul?de.
The procedure followed was substantially the same as
6.88 g. of the 2,4-dinitrophenylhydrazone derivative. The
yield of derivative indicated a yield of puri?ed benzil of
20 that used in Example I. Following this procedure a sub
27.4% and a purity of 76.9% for the crude product.
stantial yield of liquid product was obtained which con
tains a substantial yield of dinaphthy-l diketone and naph
Example III
thonitrile.
In still another experiment the reaction conditions
were varied slightly in the preparation of benzil. In this
.
This process is generally operative for the preparation
of aromatic 1,2-diketones and the corresponding aryl ni
experiment 2.97 g. of cyanogen was bubbled into a mix
ture of benzene and A1013. The procedure in this case
triles.
differed from the procedure of Example I in that the mix
relatively inert functional substituents) may be reacted
ture with aqueous H01 was re?uxed for70‘ minutes during
the hydrolysis step. This change in procedure lowered
the yield slightly. In this experiment 5.60 g. of crude
product was obtained and converted to the 2,4-dinitro
phenylhydrazone derivative. Based on the amount of
the derivative obtained, the yield of pure benzil was
29.4%, and the crude product had a purity of 63.1%.
In each of Examples I, II, and HI there is also obtained
a ‘by-product, benzonitrile, in a yield about the same as
In this process any aromatic hydrocarbon or its
equivalent (derivatives of aromatic hydrocarbons having
with cyanogen in the manner described above. The reac
30 tion requires an aromatic hydrocarbon-cyanogen ratio of
at least 2:1 and further requires the presence of an an
hydrous mixed catalyst consisting of an aluminum halide,
such as aluminum chloride or aluminum bromide, and a
hydrogen halide such as hydrogen chloride or hydrogen
35 rbromide. The aluminum halide catalyst must be present
. in no less than an equal molar’ amount relative to the
cyanogen reacted. If a lesser proportion of the aromatic
hydrocarbon or the aluminum halide catalyst is used a
different reaction product is obtained.
In still another experiment the procedure was varied by 40 While we have described several preferred embodiments
, of this invention and have described the invention fully
eliminating the use of I-ICl in the reaction. In this ex
and completely as required by the patent laws, we wish
- periment benzene and AlCla were mixed and 3.05 g. of
it understood that within the scope of the appended claims
cyanogen bubbled into the mixture. The cyanogen-con
this invention may be practiced otherwise than as speci?~
taining mixture was then re?uxed for 30 minutes and al
'
lowed to cool. After cooling, aqueous HCl was added 45 cally described.
What is claimed is:
1
to the mixture and the resulting mixture re?uxed for 70
1. A method of preparing aromatic 1,2-diketones an
minutes. The aqueous layer from’ this step was extracted
aryl nitriles which comprises reacting an aromatic hydro
with ether and combined with the benzene layer from the
carbon with cyanogen in a mol ratio ‘not less than about
hydrolysis step. The combined ether and benzene solu
tion was Water-washed until free of acid, and the solvent 50 72:1, in the presence of a catalyst consisting essentially of
anhydrous mixture of an aluminum halide of the group
was evaporated therefrom, leaving 3.09 g. of crude prod
consisting of aluminum chloride and aluminum bromide
uct. This product did not have the appearance of benzil
and a hydrogen halide of the group consisting of hydrogen
and did not melt in the range of the melting point of ben
chloride and hydrogen ‘bromide vat an aluminum halide
zil. Furthermore, this product did not form a derivative
with 2,4-dinitrophenylhydrazone, which indicated that the 55 cyanogen molar ratio of at least 1, and hydrolyzing the
reaction product to produce a mixture containing an arc
product obtained in this experiment was not benzil.
matic 1,2-diketone and an 'aryl nitrile.
Example V
2. A method according to claim 1 in which the aromatic
hydrocarbon reactant is of the group consisting of hen
The preparation of tolunitrile and tolil was carried out
in a 500 ml., 3-necked ?ask equipped with a gas-bubbling 60 zene, toluene, xylene, and naphthalene.
3. A method according to claim 1 in which the catalyst
tube, a mercury-sealed stirrer, and a condenser. To the
’ comprises an anhydrous mixture of aluminum chloride
?ask there were charged 54 g. (0.41 mol) of anhydrous
and hydrogen chloride.
aluminum chloride and 2.00 ml. (1.88 mol) of QR tolu
4. A method according to claim 1 in which the aro-r
ene. A gaseous mixture of cyanogen (40 cc./min.) and
the yield of benzil.
'
'
Example IV
nitrogen (40 cc./rnin.) was bubbled in, with stirring, for 65 matic hydrocarbon is re?uxed during the reaction with
40 minutes during which time the temperature was slowly
raised to 40° C. The cyanogen flow was stopped (after
addition of 0.065 mol) and hydrogen chloride (75
. 1
cyanogen.
5. A method according to claim 3 in which the aro
matic hydrocarbon is benzene and the reaction products
comprise a mixture of benzil and benzonitrile.
cc./min.) was charged with the nitrogen for additional
75 minutes (thus adding 0.23 mol of HCl). The tem 70 6. A method according to claim 3 in which the aro
matic hydrocarbon is toluene ‘and the reaction products
perature was gradually raised to 80° C. Then nitrogen
alone was bubbled in for an additional hour.
The reac
tion mixture was cooled overnight and then poured on a
' are a mixture of tolil and tolunitrile.
7. A method according to claim 3 in which the aro
matic hydrocarbon‘is xylene and the reaction products ob
toluene layer was water-washed until neutral, ?ltered and 75 tained are a mixture of xylil and xylonitrile.
mixture of ice and concentrated hydrochloric acid. The
.
5
8. A method according to claim 3 in which the aro
matic hydrocarbon is naphthalene in solution in an inert
solvent and the reaction products are a mixture of di
naphthyl 1,2-diketone and naphthyl nitrile.
9. A method according to claim 3 in which cyanogen is 5
added to a large molar excess of benzene and anhydrous
aluminum chloride at ambient temperature, anhydrous hy
drogen chloride is bubbled into the mixture, the mixture
is re?uxed, and the product obtained is hydrolyzed with
concentrated hydrochloric acid and ice to produce a mix 10
ture of benzonitn'le and benizil.
10. A method according to claim 6 for preparing tolu
nitrile and tolil which comprises mixing toluene and an
hydrous aluminum chloride at room temperature, bub
6
perature to about 40° C., heating the mixture of reactants
to about 80° C. and bubbling anhydrous hydrogen chlo
ride therethrough, and hydrolyzing the resulting reaction
products to produce a mixture or“ tolil and tolunitrile.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,789,995
Johnston ____________ __ Apr. 23, 1957
OTHER REFERENCES
Vorlander: Chemical Abstracts, vol. 5, 1911, page 3817.
Migrdichian: “The Chemistry of Organic Cyanogen
bling cyanogen into the mixture and increasing the tem 15 Compounds,” 1947, p. 247.
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